The present invention relates to a microlens array substrate, a method of manufacturing the same, and a display device.
A microlens array formed by a number of micro lenses arranged side by side has been applied to liquid crystal panels, for example. Each lens of the microlens array converges incident light upon each pixel to illuminate a display screen.
As a method of manufacturing a microlens array, methods using dry etching or wet etching have been known. However, these methods require a lithographic step each time when manufacturing an individual microlens array, thereby leading to increased costs.
Therefore, a method of manufacturing a microlens array by dripping a liquid resin onto a master mold having curved surfaces corresponding to lenses and removing the solidified resin has been developed as disclosed in Japanese Patent Application Laid-Open No. 3-198003.
A microlens array illuminates a display screen, but contrast between pixels is not improved by a conventional microlens array. A means for improving contrast is required in addition to a microlens array in order to provide a bright and vivid display on the screen. However, a conventional method of manufacturing a microlens array has given no attention to the improvement of contrast.
The present invention has been achieved to solve the above problem, and an objective of the present invention is to provide a microlens array substrate capable of improving contrast in addition to illuminating a screen, a method of manufacturing the same, and a display device.
(1) A method of manufacturing a microlens array substrate according to the present invention comprises the steps of:
closely providing a substrate precursor between a first master mold having a plurality of curved surfaces and a second master mold having a plurality of projections to form a substrate having a plurality of lenses formed by the curved surfaces and recesses formed by the projections;
removing the first and second master molds from the substrate; and
filling the recesses with a shading material after the second master mold is removed.
According to the present invention, the substrate precursor is closely placed between the first and second master molds and the lenses are formed by transferring the shapes of the curved surfaces of the first master mold. A microlens array substrate having a plurality of lenses can be thus easily formed. Because each lens converges incident light, a display screen can be brightly illuminated. Moreover, because the first and second master molds can be used repeatedly as long as durability permits, the step of producing these master molds can be omitted in the steps of manufacturing the second and subsequent microlens array substrates, thereby reducing the number of steps and production costs.
The recesses are formed on the microlens array substrate by transferring the-shapes of the projections of the second master mold, and the recesses are filled with the shading material. The shading material functions as a black matrix to improve contrast between pixels.
According to the present invention, a microlens array substrate capable of improving contrast in addition to illuminating brightly a display screen can be easily manufactured by transferring.
(2) In this manufacturing method, the substrate precursor may be closely placed between the first and second master molds such that each of the projections avoids being positioned right above the center of each of the curved surfaces.
Since each of the recesses on the microlens array substrate avoids being positioned right above the center of each of the lenses, a black matrix can be formed so as to avoid the center of the lenses.
(3) This manufacturing method may further comprise a step of forming a protective film by placing a protective film precursor on at least one of the shading material in the recesses and the lenses, and by solidifying the protective film precursor.
(4) The protective film precursor may be of a material which can be cured by applying energy.
(5) The energy may be at least one of light and heat.
(6) The protective film precursor may be a UV-curable resin.
(7) In this manufacturing method, the protective film precursor may be solidified after placing a reinforcing plate on the protective film precursor.
(8) The substrate precursor may be of a material which can be cured by applying energy.
By using such a material, the substrate precursor can be easily provided to minute parts of the first and second master molds, and so a microlens array substrate formed by precisely transferring the shapes of the curved surfaces and projections of the first and second master molds can be provided.
(9) The energy may be at least one of light and heat.
Therefore, a commonly used exposure apparatus, baking furnace, or hot plate can be used, thereby reducing facility costs and space.
(10) The substrate precursor may be a UV-curable resin.
As the UV-curable resin, an acrylic resin is preferable -because of superior transparency and availability of various commercial resins and photosensitizers
(11) In this manufacturing method, the recesses may be filled with the shading material by an ink jet method.
According to the ink jet method, the shading material can be provided at a high speed with no waste.
(12) In this manufacturing method, at least part of an inner surface of each of the recesses may be tapered such that an opening portion is wider than a bottom portion.
Since the tapered recesses can be reliably filled with the shading material, thus produced microlens array substrate is particularly suitable for a liquid crystal panel with high resolution.
(13) In this manufacturing method, only the opening portion of the inner surface may be tapered.
Such recesses permit only a small difference in thickness of the shading material, thereby ensuring uniform shading performance. The microlens array thus manufactured can provide a vivid image.
(14) A microlens array substrate according to the present invention comprises: a plurality of lenses formed on one surface of the microlens array substrate; a plurality of recesses formed on the other surface of the microlens array substrate such that each of the recesses avoids being positioned right above the center of each of the lenses; and a shading layer formed in the recesses.
According to the present invention, each lens converges incident light upon each pixel to brightly illuminate a display screen, and the shading layer formed in the recesses functions as a black matrix to improve contrast between pixels.
(15) The microlens array substrate may further comprise a protective film on at least one of the lenses and the shading layer.
(16) The microlens array substrate may further comprise a reinforcing plate on the protective film.
(17) In the microlens array substrate, at least part of an inner surface of each of the recesses may be tapered such that an opening portion is wider than a bottom portion.
Because the opening portion is wider than the bottom portion and the recesses can be reliably filled with the shading material, the microlens array substrate is particularly suitable for a liquid crystal panel with high resolution.
(18) In the microlens array substrate, only the opening portion of the inner surface may be tapered.
Such recesses permit only a small difference in thickness of the shading material, thereby ensuring uniform shading performance, and a vivid image can be provided.
(19) A microlens array substrate according to the present invention is manufactured by the above-described method.
(20) A display device according to the present invention comprises the above-described microlens array substrate and a light source which emits light toward the microlens array substrate, wherein the microlens array substrate is placed such that a surface on which the lenses are formed faces the light source.
(21) The relation between the light refractive index xe2x80x9cnaxe2x80x9d of the material forming the microlens array substrate and the light refractive index xe2x80x9cnbxe2x80x9d outside the lenses may be xe2x80x9cna greater than nbxe2x80x9d, when the lenses are convex lenses.
When light passes from a medium with a lower refractive index to a medium with a higher refractive index, the light is refracted to a direction approaching the normal line of the interface between the two media. When the relation between xe2x80x9cnaxe2x80x9d and xe2x80x9cnbxe2x80x9d satisfies xe2x80x9cna greater than nbxe2x80x9d, the incident light can be converged by using convex lenses.
(22) The relation between the light refractive index xe2x80x9cnaxe2x80x9d of the material forming the microlens array substrate and the light refractive index xe2x80x9cnbxe2x80x9d outside the lenses may be xe2x80x9cna less than nbxe2x80x9d, when the lenses are concave lenses.
When light passes from a medium with a higher refractive index to a medium with a lower refractive index, the light is refracted to a direction away from the normal line of the interface between the two media. When the relation between xe2x80x9cnaxe2x80x9d and xe2x80x9cnbxe2x80x9d satisfies xe2x80x9cna less than nbxe2x80x9d, the incident light can be converged by using concave lenses.